Reinforcement for a composite turbine blade of a turbomachine, comprising a stack of plies

Abstract

This application relates to a reinforcement (6) for a turbine blade (1) of a turbomachine (100), the blade (1) comprising a first outer skin (2) and a second outer skin (3) of composite material, each comprising an inner end portion (21, 31) spaced apart to define between them an inner cavity (4) of the blade (1) opening into an opening (5), wherein the reinforcement (6) is adapted to be arranged in the inner cavity (4) so ​​as to close the opening (5), and wherein the reinforcement (6) comprises a stacking of superimposed plies (61) in a stacking direction (De) corresponding to a thickness direction (Pe) of the plies (61), at least two plies (61) having different lengths (Pl) and / or widths (PL) such that the reinforcement (6) has a profile of variable dimensions. Figure for the abstract: Fig. 3a

Description

Title of the invention: Reinforcement for a composite blade of a turbomachine, comprising a stack of plies Technical field

[0001] The present application relates to aircraft turbomachines, in particular turbojets or turboprops. The application relates to a reinforcement for a composite turbomachine blade, a composite blade provided with such a reinforcement, and a method for manufacturing such a reinforcement and such a composite blade. TECHNOLOGICAL BACKGROUND

[0002] An aircraft conventionally comprises at least one turbomachine to provide propulsion.

[0003] The turbomachine comprises at least one fan or propeller, at least one compressor, a combustion chamber, at least one turbine, and a gas exhaust nozzle. For example, the turbomachine may comprise a low-pressure compressor and a high-pressure compressor, and a high-pressure turbine and a low-pressure turbine. The high-pressure turbine rotates the high-pressure compressor via a high-pressure shaft, and the low-pressure turbine rotates the low-pressure compressor via a low-pressure shaft. The low-pressure turbine may also rotate the fan either directly via the low-pressure shaft or via a reduction gear arranged between the low-pressure turbine and the fan, the reduction gear being rotated by the low-pressure shaft.

[0004] The fan comprises a hub and blades secured to the hub, the fan blades being rotatable about a longitudinal axis of the turbomachine. A secondary flow straightener may be arranged downstream of the fan. The straightener comprises straightener blades located downstream of the fan blades, the straightener blades being static, i.e. being fixed in rotation relative to the longitudinal axis of rotation of the fan blades.

[0005] In a shrouded turbomachine, or turbojet, the fan is housed in a fan casing, upstream of the rest of the turbomachine.

[0006] In an unducted turbomachine, or turboprop, (in English "Open rotor" or "Unducted fan"), the fan is an unducted propeller placed outside the nacelle, in the air flow surrounding the turbomachine. An unducted turbomachine may comprise two unducted and counter-rotating fans, or propellers (known by the English acronym UDF for "UnDucted Fan"), or alternatively a single unducted fan and a rectifier comprising several rectifier blades (known by the English acronym USF for "Unducted Single Fan"). The fan can be placed at the rear of the gas generator so as to be of the pusher type or at the front of the gas generator so as to be of the tractor type. An unducted turbomachine makes it possible to increase the bypass ratio very significantly without being penalized by the mass of the casings or nacelles intended to surround the fan blades.

[0007] The turbomachine may be a dual-flow turbomachine, in which the mass of air drawn in by the fan is divided into a primary flow, which passes through the at least one compressor, the combustion chamber and the at least one turbine, and a secondary flow, which is concentric with the primary flow. The bypass ratio of a turbomachine corresponds to the ratio between the flow rate of the primary flow and the flow rate of the secondary flow. Increasing the bypass ratio makes it possible to improve the performance of the turbomachine and to reduce its specific fuel consumption. This results in an increase in the diameter of the blades at iso engine thrust, in particular the blades of the fan and the blades of the associated rectifier. This increase in dimensions is even greater for unducted turbomachines, in which the blades are larger and the rotational speeds are lower.The increase in blade dimensions leads to an increase in blade mass, particularly the stator blades, which is detrimental to the performance of the turbomachine.

[0008] In order to reduce the mass of the blades, the blades may be designed from an organic matrix composite material comprising a fibrous reinforcement embedded in an organic matrix. In addition, the organic matrix may be partially hollow, reinforcing only the structural parts.

[0009] Known from the prior art, as illustrated in [Fig.l], is a rectifier blade 100 of a shrouded turbomachine extending radially between an internal platform, by which the blade 100 is fixed to an internal casing of the turbomachine, and an external platform, by which the blade 100 is fixed to an external casing of the turbomachine. Each blade 100 comprises a blade body made of composite material consisting of a fiber reinforcement having a three-dimensional weave and densified by a matrix. The fiber reinforcement has an end portion comprising two segments 200 detached from each other up to a free end of the fiber reinforcement. The blade 100 further comprises a filling sub-component (“Gap filler” or “roving” in English) in the form of an added insert 300 making it possible to fill a free space at the junction between the segments 200 of the fiber reinforcement. The insert 300 can in particular be manufactured from a shaped braid.Document FR 3 063 514 A1 describes such a rectifier blade, the blade further comprising an added insert having a pi-shaped section. Thus, the blade can be manufactured from a composite material. solid instead of metallic materials such as titanium, and the increase in blade mass is reduced.

[0010] However, the added insert does not make it possible to meet the new geometric and structural constraints of a composite blade, in particular a 3D woven organic matrix composite blade of a secondary flow straightener. Indeed, the evolution of the target geometry of the added insert, which must have a very significant variation in thickness, makes it impossible to manufacture it using known techniques, such as from a shaped braid.

[0011] Furthermore, in unducted turbomachines, the fact of fixing the blade, in particular the stator blade, to a casing of the turbomachine only by its internal radial end located at the blade root, has the consequence of transmitting all the forces in the area of ​​the blade root, which results in high levels of stresses in the composite parts of the blade root. The known inserts do not allow the blade root area to be sufficiently reinforced locally, and thus do not sufficiently limit the opening and the stresses at the level of the loose segments of the fiber reinforcement under tensile, compressive and bending stresses. Furthermore, the known inserts manufactured from a braid have too low a rigidity and therefore do not allow the overall stiffness of the blade to be sufficiently increased, which leads to an increased risk of buckling and a degradation of the frequency placement of the stator. Statement of the invention

[0012] An aim of the present application is to propose a reinforcement for a composite turbomachine blade making it possible to reduce the stresses exerted on the blade at a structural zone of the blade, and making it possible to limit the increase in the mass of the blade.

[0013] Another aim of the application is to propose a reinforcement for a composite turbomachine blade having a complex geometry and satisfactory mechanical resistance properties.

[0014] Another aim of the application is to propose a method for manufacturing such a reinforcement which makes it possible to quickly create a reinforcement having a complex geometry.

[0015] To this end, according to a first aspect, a reinforcement is proposed for a turbomachine blade, the blade comprising a first outer skin and a second outer skin made of composite material connected to each other at an outer end of the blade, the first skin comprising a first inner end portion, the second skin comprising a second inner end portion, the first inner end portion and the second inner end portion being spaced apart from each other so as to delimit between them an inner cavity of the blade. opening into an opening at an inner end of the blade, the inner end being radially opposite the outer end, wherein the reinforcement is adapted to be arranged in the inner cavity so as to plug the opening, and wherein the reinforcement comprises a stack of plies, each ply having a length, a width and a thickness, a ply being superimposed on an adjacent ply in a stacking direction corresponding to a direction of the thickness of the plies, at least two of the plies of the stack having different lengths and / or widths so that the reinforcement has a profile of variable dimensions.

[0016] Optionally, the stack of plies of the reinforcement may comprise a first ply having a first length and a second ply having a second length strictly less than the first length, and: - the second ply may be arranged closer to a center of the reinforcement than the first ply, the stacking direction being adapted to correspond to a thickness direction of the blade, or - the first ply may be adapted to be disposed closer to the inner end of the blade than the second ply when the reinforcement is disposed in the inner cavity of the blade, the stacking direction being adapted to correspond to a height direction of the blade.

[0017] According to a second aspect, the present application relates to a turbomachine blade, comprising a first outer skin and a second outer skin made of composite material connected to each other at an outer end of the blade, the first skin comprising a first inner end portion, the second skin comprising a second inner end portion, the first inner end portion and the second inner end portion being spaced apart from each other so as to delimit between them an inner cavity of the blade opening into an opening at an inner end of the blade, the inner end being radially opposite the outer end, the blade further comprising a reinforcement according to the first aspect, the reinforcement having dimensions corresponding substantially to dimensions of the inner cavity at the opening, the reinforcement being arranged in the inner cavity so as to block the opening.

[0018] Some preferred but non-limiting features of the blade according to the second aspect are the following, taken individually or in any technically conceivable combination:

[0019] - the blade comprises a blade with an aerodynamic profile suitable for being placed in a flow of air when the turbomachine is in operation in order to generate lift, and a root configured to be fixed to the hub of a blade comprising the blade at the inner end of the blade, the first inner end portion and the second inner end portion being adapted to together define outer walls of the root and at least a portion of the blade of the blade, such that the inner cavity comprises a root portion and a blade portion, and the reinforcement comprising a root portion disposed in the root portion of the inner cavity and a blade portion disposed in the blade portion of the inner cavity;

[0020] - the blade further comprises a filling material disposed in the cavity in radially inner between the reinforcement and the outer end of the blade.

[0021] According to a third aspect, the present application relates to an unducted turbomachine, comprising: - a casing; - a fan having a fan hub and peripheral fan blades, integral with the fan hub, the fan hub having a downstream hub portion which is surrounded by an internal surface of an upstream portion of the casing and which projects from the upstream portion of the casing, the fan hub being rotatably mounted relative to the upstream portion of the casing about the longitudinal axis; and - at least one rectifier blade according to the second aspect, said blade being located downstream relative to the peripheral fan blades, said blade being mounted on an external surface of the upstream part of the casing at an internal end of the blade, the reinforcement being arranged at the internal end of the blade.

[0022] According to a fourth aspect, the present application relates to a method of manufacturing a reinforcement according to the first aspect for a turbomachine blade, comprising the following steps: El: Cutting a set of plies in a carbon mat, each ply having a length, a width and a thickness, at least two of the plies of the set having different lengths and / or widths; E3: Stacking of the plies of the assembly by superimposing a ply on an adjacent ply along a direction of the thickness of the plies, so as to create a stack presenting a profile of variable dimensions; and E4: Compaction of the stack of folds.

[0023] Optionally, the method may further comprise the following steps: E2: Moistening of the folds after the cutting step E1 and before the stacking step E3; and E5: Drying of the stack of compacted folds during step E4;

[0024] Optionally, the plies may be stacked during step E3 in a forming mold, the plies may be compacted during step E4 in the forming mold, and the method may further comprise a step E6 of cold demolding of the compacted stack of plies.

[0025] According to a fifth aspect, the application relates to a method of manufacturing a turbomachine blade according to the second aspect, comprising the following steps:

[0026] Production of a composite preform of the composite blade, said preform comprising a first outer skin and a second outer skin made of composite material connected to each other at an outer end of the blade, the first skin comprising a first inner end portion, the second skin comprising a second inner end portion, the first inner end portion and the second inner end portion being spaced apart from each other so as to delimit between them an inner cavity of the blade opening into an opening at an inner end of the blade, the inner end being radially opposite the outer end; Manufacturing a reinforcement by means of a method according to the fourth aspect, the reinforcement having dimensions substantially equal to dimensions of the interior cavity at the opening; Placing the reinforcement in the inner cavity of the blade preform so as to seal the opening; and Resin injection into the assembly including the blade preform and reinforcement. DESCRIPTION OF FIGURES

[0027] Other characteristics, aims and advantages will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0028] [Fig.l] illustrates a schematic perspective view in section of a blade according to the prior art.

[0029] [Fig.2] illustrates a schematic perspective view of a reinforcement according to one embodiment, the reinforcement having a second geometry different from the first geometry.

[0030] [Fig.3a] illustrates a schematic radial cross-sectional view of a blade according to one embodiment.

[0031] [Fig.3b] illustrates a schematic view in radial longitudinal section of a blade according to one embodiment.

[0032] [Fig.4a] illustrates a schematic view in radial cross-section of an end portion of a blade comprising a reinforcement according to one embodiment, the reinforcement comprising plies stacked in a stacking direction De corresponding to a thickness direction of the blade.

[0033] [Fig.4b] illustrates a schematic radial cross-sectional view of an end portion of a blade comprising a reinforcement according to one embodiment, the reinforcement comprising plies stacked in a stacking direction De corresponding to a radial direction of the blade.

[0034] [Fig.5] illustrates a partial schematic perspective view of a blade according to a embodiment.

[0035] [Fig.6] illustrates a schematic perspective view of an example of an unducted turbomachine comprising a blade according to one embodiment.

[0036] [Fig.7] is a block diagram illustrating a method of manufacturing a blade according to one embodiment. DETAILED DESCRIPTION Turbomachine

[0037] In the present application, upstream and downstream are defined relative to the normal flow direction of the gas through the fan 200 of the turbomachine 100, an airflow flowing in the turbomachine 100 from upstream to downstream. The longitudinal axis X corresponds to an axis of rotation of the fan 200. A radial axis is an axis perpendicular to the longitudinal axis X and passing through it. A longitudinal direction, respectively radial, corresponds to the direction of the longitudinal axis X, respectively radial. The terms internal and external, respectively, are used with reference to a radial direction such that the internal part or face of an element is closer to the longitudinal axis X than the external part or face of the same element.A width direction L of the blade 1 corresponds substantially to the longitudinal direction, a height direction R of the blade 1 corresponds to the radial direction at the level of the blade 1, and a thickness direction Y of the blade 1 corresponds to the direction perpendicular to the width direction L and to the height direction R of the blade 1.

[0038] The turbomachine 100 extends substantially around the longitudinal axis X. The turbomachine 100 comprises, from upstream to downstream in the direction of gas flow, at least one fan 200, or propeller, an engine assembly 300 comprising at least one compressor, a combustion chamber and at least one turbine, and a gas exhaust nozzle 108. For example, the engine assembly 300 of the turbomachine 100 may comprise a fan and a rectifier, a low-pressure compressor and a high-pressure compressor, the combustion chamber, and a high-pressure turbine and a low-pressure turbine. The high-pressure turbine rotates the high-pressure compressor via a high-pressure shaft extending along the longitudinal axis X. The low-pressure turbine rotates the low-pressure compressor via a low-pressure shaft extending along the longitudinal axis X.The low pressure turbine can also drive the fan 200 in rotation either directly via the low pressure shaft or via a reducer arranged between the low pressure turbine and the fan 200, the reducer being driven in rotation by the low pressure shaft.

[0039] Each compressor and each turbine may comprise one or more stages, each stage being formed by a set of fixed blades, or stator blades, and a set of rotating blades, or rotor blades. The fixed blades are fixed to a casing 101 of the turbomachine 100. The rotating blades of the low-pressure compressor and the low-pressure turbine are fixed to the low-pressure shaft. The rotating blades of the high-pressure compressor and the high-pressure turbine are fixed to the high-pressure shaft.

[0040] In operation, air flows through the rotating fan 200 and a first portion, called the primary flow, of the air flow is conveyed through the low-pressure compressor and the high-pressure compressor, the primary flow thus being compressed and then sent to the combustion chamber. The hot combustion products from the combustion chamber are used to drive the high-pressure turbine and the low-pressure turbine and thus produce the thrust of the turbomachine 100, and are discharged through the nozzle 108 located downstream of the engine assembly 300. A second portion of the air, called the secondary flow, is discharged from the rotating fan 200 around the casing 101 from upstream to downstream.

[0041] A blade 1 is a structural part of the turbomachine 100, intended to be integrated into a blading of the turbomachine 100. The blading comprises a hub which can be rotatably mounted relative to the casing 101 of the turbomachine 100 for a rotating blading, or be fixedly mounted relative to the casing 101 of the turbomachine 100 for a fixed blading. The blading further comprises a plurality of blades 1 fixed to the hub. The blades 1 extend substantially radially relative to the longitudinal axis X and can be distributed circumferentially around the longitudinal axis X.

[0042] The blading may have, for example, a diameter greater than or equal to 150 cm, preferably greater than or equal to 200 cm, for example less than or equal to 400 cm. Thus, the blade 1 has a sufficient span so that the blades 1 of the blading comprise two outer skins 2, 3 made of a composite material and delimiting an inner cavity 4. A blade 1 of the blading thus preferably has a height greater than or equal to 50 cm, preferably greater than or equal to 70 cm, for example of the order of 80 cm to 100 cm, being for example less than or equal to 160 cm.

[0043] [Fig. 6] illustrates a non-limiting example in which the turbomachine 100 is an unducted turbomachine whose rectifier comprises a blade 1 comprising a reinforcement 6 according to a particular embodiment. The turbomachine 100 comprises: - a casing 101; - a fan 200 having a fan hub 201 and peripheral blades 202 of the fan 200, secured to the fan hub 201, the fan hub 201 having a downstream portion 203 of the hub 201 which is surrounded by an internal surface 102 of an upstream portion 103 of the casing 101 and which protrudes from the upstream portion 103 of the casing 101, the hub 201 of the fan 200 being mounted to rotate relative to the upstream part 103 of the casing 101 around the longitudinal axis X; and - at least one rectifier blade 1, said blade 1 being located downstream relative to the peripheral blades 202 of the fan 200, said blade 1 being mounted on an external surface of the upstream part 103 of the casing 101 at an internal end of the blade 1, said blade 1 comprising a reinforcement 6 as described below, the reinforcement 6 being arranged at the internal end of the blade 1.

[0044] The casing 101 of the turbomachine 100 carries the fan 200 on its upstream side. The peripheral blades 202 of the fan 200 are distributed on the hub 201 of the fan 200 around the longitudinal axis X of rotation upstream of the casing 101 of the turbomachine 100. The hub 201 of the fan 200 is able to rotate on itself relative to the upstream part 103 of the casing 101 around the longitudinal axis X. The turbomachine 100 comprises, downstream of the hub 201 of the fan 200 and in the casing 101, a motor assembly 300 making it possible to rotate the hub 201 of the fan 200 and therefore the peripheral blades 202 of the fan 200 around the longitudinal axis X.

[0045] The rectifier vanes 1 are located in the flow space of the secondary flow, which is created downstream of the peripheral blades 202 of the fan 200 around the outer surface of the casing 101, when the peripheral blades 202 of the fan 200 are rotated around the longitudinal axis X.

[0046] The turbomachine 100 being unducted, each secondary flow straightener blade 1 is fixed or mounted in a movably manner on an outer surface of the upstream part 103 of the casing 101, only at an inner end 11 of the blade. An outer end 12 of the blade 1, which is radially opposite relative to the inner end 11, is left bare in the secondary flow, without being mounted or fixed to a casing, no casing or nacelle surrounding the straightener blades 1 and the casing 101.

[0047] The engine assembly 300 is located in the casing 101. An air inlet is located between the upstream portion 103 of the casing 101 and the hub 201 of the fan 200 and downstream of the peripheral blades 202 of the fan 200. The rectifier vane 1 has a shape configured to concentrate the secondary flow against the outer surface of the downstream portion 107 of the casing 101, located downstream of the outer surface of the upstream portion 103 of the casing 101. An external attachment arm or an external attachment means connects the casing 101 to an aircraft.

[0048] It is understood that the reinforcement 6 may be a reinforcement 6 for a blade 1 of a turbomachine 100 of any type, for example of an unducted turbomachine 100, for example of a UDF type turboprop comprising two unducted and counter-rotating fans, or of a USF type turboprop comprising a single unducted fan and a rectifier. Alternatively, the reinforcement 6 may be a reinforcement 6 for a blade 1 of a ducted turbomachine 100, for example of a turbojet comprising a ducted fan 200.

[0049] Furthermore, it is understood that the reinforcement 6 may be a reinforcement 6 for any composite blade 1 of a turbomachine 100 requiring a thick reinforcement 6 or a geometry with progressive thickness, in particular for a blade 1 made of a partially hollow organic matrix composite having a structural hollow zone to be reinforced. Thus, the reinforcement 6 may be a reinforcement 6 for a composite blade 1 of any blade of a turbomachine 100, for example a reinforcement 6 for a blade 1 of a fan 200, a rectifier, a compressor, and / or a turbine. Dawn

[0050] A blade 1 comprises a blade 13 with an aerodynamic profile suitable for being placed in an air flow when the turbomachine 100 is in operation in order to generate lift, and a root 14 configured to be fixed to the rotating or fixed hub of the blading comprising the blade 1 at the internal end 11 of the blade 1. The internal end 11 of the blade 1 thus corresponds to the mounting side of the blade 1.

[0051] The root 14 of the blade 1 may be fixed to the hub, fixed or rotating, of the blading, by a fastener receiving the root 14 of the blade 1 and fixing it to the hub of the blading. [Fig. 5] illustrates by way of non-limiting example an example of a fastener comprising holes 210, 310 passing respectively through the first internal end portion 21 and the second internal end portion 31 in the radial direction R, and which may comprise bolting or riveting in the holes, or others.

[0052] The root 14 of the blade 1 corresponds to the part of the blade 1 which is located under a line Fs delimiting the flow space of the secondary flow of the turbomachine 100, or secondary flow line Fs. Thus, the root 14 of the blade 1 is located in a radially internal position relative to a wall of the casing 101 of the turbomachine 100 which radially delimits the flow space of the secondary flow on the inside. In a ducted turbojet engine 100, the secondary flow flow space is a secondary flow vein delimited on the inside by the wall of the casing 101, the casing 101 corresponding to an inner casing, and delimited on the outside by a wall of an outer casing of the turbojet engine 100. In a turboprop 100, the secondary flow flow space is a space outside the turboprop engine 10, which is delimited on the inside by the wall of the casing 101.

[0053] The wall of the casing 101 may be formed from one or a set of inter-blade platforms 1. The inter-blade platforms 1 may be formed in a single piece with the blades 1 or be separated and attached to the blades 1 of a blading at a junction between the root 14 of the blade 1 and the blade 13. The inter-blade platforms 1 delimit inside the flow space of the secondary flow at the blading.

[0054] The aerodynamically profiled blade 13 has a leading edge 8 and a trailing edge 9. connected by an intrados wall and an extrados wall. The leading edge 8 of the blade 13 forms an upstream end of the blade 13 in the flow space. It corresponds to the front part of an aerodynamic profile which faces the air flow and which divides the air flow into an intrados flow and an extrados flow. The leading edge 8 of the blade 13 is configured to extend opposite the flow of gases entering the turbomachine 100. The trailing edge 9 of the blade 13 corresponds to the rear part of the aerodynamic profile, where the intrados and extrados flows meet, and forms a downstream end of the blade 13 in the flow space.

[0055] The blade 1 comprises a first outer skin 2 and a second outer skin 3 made of composite material, connected to each other at the outer end 12 of the blade 1. The first skin 2 and the second skin 3 extend generally opposite each other. The first skin 2 can form the intrados wall of the blade 13 and the second skin 3 can form the extrados wall of the blade 13. The skins 2 and 3 form the outer surface of the blade 1, located in the secondary air flow during operation of the turbomachine 100. The first skin 2 and the second skin 3 carry the leading edge 8 and the trailing edge 9 of the blade 1.

[0056] The first skin 2 and the second skin 3 of the blade 1 are made of a composite material comprising a fibrous reinforcement densified by a matrix. The skins 2, 3 may be monolithic and be made in a single piece from a fibrous preform with a varying thickness. Alternatively, the fibrous reinforcement may comprise a first skin 2 and a second skin 3, which are connected for example near the outer end 12 of the blade 1. The fibrous reinforcement comprises a blade portion intended to form the blade 13 with an aerodynamic profile, and a root portion intended to form the root 14 of the blade 1.

[0057] The fiber reinforcement may comprise woven or knitted three-dimensional fiber arrangements. It is further made such that it comprises strands (i.e. any type of yarn(s)) that extend continuously both inside the blade portion 13 and inside the root portion 14 of the blade 1. Alternatively, the fiber reinforcement may comprise laminated two-dimensional fiber arrangements. The fibers of the fiber reinforcement comprise at least one of the following materials: carbon (typically silicon carbide), glass, aramid, polypropylene and / or ceramic (typically an oxide ceramic). The matrix typically comprises an organic matrix (thermosetting, thermoplastic or elastomer) or a carbon matrix. For example, the matrix comprises a plastic material, typically a polymer, for example epoxy, bismaleimide or polyimide.

[0058] The first skin 2 comprises a first inner end portion 21 and the second skin 3 comprises a second inner end portion 31. The first inner end portion 21 and the second inner end portion 31 are distant from one another so as to delimit between them an internal cavity 4 of the blade 1 opening into an opening 5 at an internal end 11 of the blade 1, the internal end 11 being radially opposite the external end 12.

[0059] The inner end 11 of the blade 1 corresponds to a mounting end of the first skin 2 and the second skin 3 on a rotating or fixed hub of the blading comprising the blade 1. The blade 1 can be fixed to the rotating or fixed hub of the blading at its inner end 11 only, in particular in the case of an unducted turbomachine 100, or at both its inner end 11 and its outer end 12, in particular in the case of a ducted turbomachine 100.

[0060] A height of the blade 1 corresponds to a distance along the radial axis between the inner end 11 and the outer end 12 of the blade 1. The outer end 12 of the blade 1 corresponds to a tip of the blade 1. A height of the blade 13 corresponds to a distance along the radial axis between an inner end and an outer end of the blade 13. A height of the root 14 corresponds to a distance along the radial axis between an inner end and an outer end of the root 14. The outer end 12 of the blade 1 corresponds to the outer end of the blade 13, and the inner end 11 of the blade 1 corresponds to the inner end of the root 14. The inner end of the blade 13 may correspond to the outer end of the root 14.

[0061] The skins 2, 3 of the fiber reinforcement are separated by the inner cavity 4 which is open at the inner end of the blade 1, which makes it possible to further reduce the mass of the blade 1 in comparison with a conventional blade 1. In the case where the skins 2, 3 are obtained by three-dimensional weaving and are monolithic, the inner cavity 4 is obtained by making a delinking in the fiber reinforcement between two successive layers of warp, from a so-called non-delinked zone (here comprising the head 12 of the blade 1) to the inner end 11 of the skins 2, 3, where the inner cavity 4 opens at the opening 5. For this, at the delinking, the warp strands of two successive layers of the fiber blank are not connected by weft strands. Preferably, the decoupling extends within the aerodynamically profiled blade 13 and extends to the inner end of the root 14 of the blade 1.

[0062] In the blade portion of the fiber reinforcement, the inner cavity 4 is not open on the leading edge 8 or the trailing edge 9. The portions of the fiber reinforcement forming the leading edge 8 and the trailing edge 9 are therefore not untied. The leading edge 8 and / or the trailing edge 9 may be attached and fixed to the fiber reinforcement, as described below concerning the method of manufacturing the blade 1. On the other hand, in the root portion of the fiber reinforcement, the inner cavity 4 may be open on the upstream and downstream edges of the root 14 of the blade 1, which extend in the extension of the leading edge 8 and the trailing edge 9 of the blade 13, respectively. The portions of the fiber blank forming the upstream edge and the downstream edge of the root 14 of the blade 1 may therefore be untied.

[0063] Reference may be made, as an example, to document EP2588758 in the name of the Applicant for further details on the production of disconnections.

[0064] The first internal end portion 21 and the second internal end portion 31 correspond to the parts of the skins 2, 3, which are located in a radially internal position relative to the delinking carried out in the fibrous reinforcement. The first internal end portion 21 and the second internal end portion 31 may extend over the entire height of the root 14 of the blade 1 and over at least a portion of the height of the blade 13 of the blade 1, or even over substantially the entire height of the blade 13 of the blade 1 when the separation is located substantially at the level of the external end 12 of the blade 1. Thus, the first internal end portion 21 and the second internal end portion 31 are adapted to together define external walls of the root 14 and of at least a portion of the blade 13 of the blade 1, so that the internal cavity 4 comprises a root portion and a blade portion.The internal cavity 4 thus extends over the entire height of the root 14 of the blade 1, and over at least part of the height of the blade 13, or even over substantially the entire height of the blade 13.

[0065] The first skin 2 and the second skin 3 can move away 101 from each other towards the inner end 11 of the blade 1 along the thickness direction Y of the blade 1. The inner cavity 4 is located in a radially external position relative to the opening 5 and thus has a maximum thickness at the opening 5, i.e. at the inner end 11 of the blade 1.

[0066] A plate 10 may be fixed under and against the first inner end portion 21 and the second inner end portion 31 and be located under and against the opening 5 and the reinforcement 6. The plate 10 makes it possible to make a connection between the first inner end portion 21 and the second inner end portion 31.

[0067] The blade 1 may be a variable-pitch stator blade. The stator comprises a hub mounted fixedly relative to the casing 101 of the turbomachine 100, and is therefore non-rotating. The stator blades 1 extend substantially radially relative to the longitudinal axis X. The blade 1 then comprises an actuating mechanism for modifying the pitch angle of the blade in order to adapt the performance of the turbomachine 100 to the different flight phases. In addition, each blade 1 comprises an attachment, or pivot, arranged at the root 14 of the blade 1. The attachment is rotatably mounted relative to the hub around the pitch axis. More precisely, the attachment is rotatably mounted inside a housing provided in the hub, by means of balls or other rolling elements. Thus, each foot 14 of the rectifier blade 1 is pivotally mounted along a setting axis and connected to a pitch change system mounted in the turbomachine 100. Reinforcement

[0068] A reinforcement 6 (in English “Spar filler”), illustrated as a non-limiting example in [Fig.2], is a sub-component of the blade 1. The reinforcement 6 is adapted to be arranged in the interior cavity 4 so as to plug the opening 5. In addition, the reinforcement 6 helps to form and / or compact the three-dimensionally woven skins.

[0069] As illustrated by way of non-limiting example in [Fig.3a] and in [Fig.3b], the reinforcement 6 comprises a stack of plies 61, each ply 61 having a length PI, a width PL and a thickness Pe, a ply 61 being superimposed on an adjacent ply 61 in a stacking direction De corresponding to a direction of the thickness Pe of the plies 61. At least two of the plies 61 of the stack have different lengths PI and / or widths PL so that the reinforcement 6 has a profile of variable dimensions.

[0070] The reinforcement 6 described above makes it possible to fill the opening 5 between the first internal end portion 21 and the second internal end portion 31, to correctly form the 3D woven skins and to provide improved mechanical strength once the part has been polymerized, in particular bending stiffness, at the internal end 11 of the blade 1 which is an area where the stresses are greatest. The reinforcement 6 therefore allows a satisfactory compromise between stiffness and mass to improve the mechanical strength of the blade 1, for example compared to the addition of a spar or compared to an increase in the thickness of the composite outer skins 2, 3.The stiffening of the area located at the internal end 11 of the blade 1 makes it possible to reduce the stresses in the composite outer skins 2, 3 in comparison with a solution whose cavity would be filled only with foam or provided with an insert as described in the document FR 3 063 514 AL The increase in stiffness also makes it possible to limit the displacement of the external end 12 of the blade 1.

[0071] At least two of the plies 61 of the reinforcement 6 have different geometries, in particular different lengths PI and / or different widths PL. Thus, the stacking of plies 61 makes it possible to create a reinforcement 6 having a significant volume and a profile, that is to say a complex geometry with large variations in dimensions, in particular large variations in thickness over a reduced height. The reinforcement 6 can thus plug the internal cavity 4 of the blade 1, in particular at an internal end 11 of the blade 1 located at the zone of attachment of the blade 1 to a casing 101 of the turbomachine 100.

[0072] Finally, the stack of plies 61 of the reinforcement 6 is simple and quick to manufacture. The plies 61 are in fact stacked by superimposing one ply 61 on a following adjacent ply 61.

[0073] The reinforcement 6 may have a rigidity greater than 15 (+ / -5) GPa in the radial direction R of the blade 1. Thus, the reinforcement 6 contributes to the overall stiffness of the blade 1, to limit the risk of buckling and improve the frequency placement of the blade. including dawn 1.

[0074] The volumetric content of fibers of the reinforcement 6 is preferably between 20% and 50%, for example between 30% and 45%, so as to ensure optimal mechanical properties of the reinforcement 6.

[0075] The reinforcement 6 may have dimensions corresponding substantially to dimensions of the interior cavity 4 of the blade 1 at the opening 5. Thus, the reinforcement 6 is arranged in the interior cavity 4 so as to block the opening 5. The reinforcement 6 may have dimensions corresponding substantially to dimensions of the interior cavity 4 over an entire height of the reinforcement 6, the reinforcement 6 being arranged in a portion of the interior cavity 4 so as to at least partially fill said interior cavity 4. More particularly, the reinforcement 6 may comprise a root portion arranged in the root portion of the interior cavity 4 and a blade portion arranged in the blade portion of the interior cavity 4.The root portion of the reinforcement 6 may have dimensions corresponding substantially to the dimensions of the root portion of the interior cavity 4 so that the root portion of the reinforcement 6 completely blocks the root portion of the interior cavity 4. The blade portion of the reinforcement 6 may have dimensions corresponding substantially to the dimensions of a portion of the blade portion of the interior cavity 4 so that the blade portion of the reinforcement 6 partially blocks the blade portion of the interior cavity 4.

[0076] The reinforcement 6 may have a downwardly flared shape, i.e. an inverted funnel shape. Thus, a shape of the reinforcement 6 corresponds substantially to a shape of the internal cavity 4 of the blade 1 at the end portions of the blade 1 which move away from each other along the thickness direction Y of the blade 1.

[0077] Each ply 61 of the stack of plies of the reinforcement 6 may comprise two opposite surfaces spaced apart from each other by the thickness Pe of ply 61 and each having a length corresponding to the length PI of ply 61 and a width corresponding to the width PL of ply 61. A surface of a ply 61 is superimposed on a surface of an adjacent ply 61 along the stacking direction De so as to form the stack. All the plies 61 of the set may have substantially the same thickness Pe.

[0078] In a first embodiment, illustrated by way of non-limiting example in [Fig.4a], the stacking direction De corresponds to the thickness direction Y of the blade 1. The plies 61 are then stacked on top of each other along the thickness direction Y of the blade 1. A thickness direction Pe of a ply 61 corresponds to the thickness direction Y of the blade 1. A length direction PI of a ply 61 may correspond to the height direction R of the blade 1, and a width direction PL of a ply 61 may correspond to the width direction L of the blade 1. Several plies 61 may have different lengths PI. A stack of several plies 61 having different lengths PI makes it possible to form a reinforcement 6 adapted for to match the shapes of an inner cavity 4 of a blade 1 which has a variable thickness, which is the case at the inner end parts 21 and 31 of the first outer skin 2 and of the second outer skin 3. This first embodiment is particularly advantageous in the case of a blade 1 for a secondary flow straightener of a turbomachine 100, because it makes it possible to improve the mechanical strength by minimizing the differences in stiffness and the coefficients of thermal expansion with the outer skins 2, 3 of the blade 1 between which the reinforcement 6 is intended to be inserted.

[0079] The stack of plies of the reinforcement 6 may comprise a first ply 611 having a first length Ply and a second ply 612 having a second length P12 strictly less than the first length Ply. In the stack of plies 61, the second ply 612 may be arranged closer to a center of the reinforcement 6 than the first ply 611. Thus, the first ply 611 of the stack is located, when the reinforcement 6 is located in the inner cavity 4 of the blade 1, closer to one of the outer skins 2, 3 of the blade 1 than the second ply 612. For a given constant height of the reinforcement 6, the first ply 611, which has a greater length Ply, may thus curve close to the inner end 11 of the blade 1, so as to match a contour of the inner cavity 4 of the blade 1, the thickness of which increases close to the inner end 11 of the blade 1.The second fold 612 is less curved than the first fold 611, or may even remain straight, i.e. not curved.

[0080] The stack of plies of the reinforcement 6 may comprise a third ply 613 having a third length P13 strictly between the first length P1 and the second length P12. The third ply 613 is arranged between the first ply 611 and the second ply 612. In general, the stack of plies of the reinforcement 6 may comprise any number of plies 61 having different lengths, the plies 61 being arranged progressively according to their length P1 so that the closer the ply 61 is to the center of the reinforcement 6, the shorter its length P1. In other words, when the reinforcement 6 is inserted into the inner cavity 4 of a blade 1, the closer the ply 61 is to an outer wall of the blade 1, the longer the ply 61 has a length P1.Thus, the longer folds curve more than the shorter folds near the inner end 11 of the blade 1, the reinforcement 6 consequently having a downwardly flared shape adapted to match a shape of the inner cavity 4 of the blade 1 at the inner end 11 of the blade 1.

[0081] In a second embodiment, illustrated by way of non-limiting example in [Fig.4b], the stacking direction De corresponds to the height direction R of the blade 1. The plies 61 are then stacked on top of each other in the height direction of the blade 1. A thickness direction Pe of a ply 61 corresponds to the direction of height R of the blade 1. A length direction PI of a ply 61 may correspond to the thickness direction Y of the blade 1, and a width direction PL of a ply 61 may correspond to the longitudinal direction L. Several plies 61 may have different lengths PI. A stack of several plies 61 having different lengths PI makes it possible to form a reinforcement 6 adapted to match the shapes of an internal cavity 4 of a blade 1 which has a variable thickness, which is the case at the internal end portions 21, 31 of the first outer skin 2 and of the second outer skin 3. This second embodiment is particularly advantageous in the case of a blade 1 having a large variation in thickness, or having a large thickness, at the internal end portions 21, 31 of the skins 2, 3.

[0082] The stack of plies of the reinforcement 6 may comprise a first ply 611 having a first length Ply and a second ply 612 having a second length P12 strictly less than the first length Ply. In the stack of plies 61, the first ply 611 is adapted to be arranged closer to the inner end 11 of the blade 1 than the second ply 612 when the reinforcement 6 is arranged in the inner cavity 4 of the blade 1. Thus, the first ply 611 of the stack is located, when the reinforcement 6 is located in the inner cavity 4 of the blade 1, closer to the opening 5 than the second ply 612. The reinforcement 6 can thus best match a contour of the inner cavity 4 of the blade 1, the thickness of which increases near the inner end 11 of the blade 1, the thickness of the cavity 4 being maximum at the opening 5.

[0083] The stack of plies of the reinforcement 6 may comprise a third ply 613 having a third length P13 strictly between the first length P1 and the second length P12. The third ply 613 is arranged between the first ply 611 and the second ply 612. In general, the stack of plies of the reinforcement 6 may comprise any number of plies 61 having different lengths, the plies 61 being arranged progressively according to their length P1 so that when the reinforcement 6 is arranged in the inner cavity 4, the closer the ply 61 is to the inner end 11 of the blade 1, the greater its length P1. Thus, the reinforcement 6 has a downwardly flared shape adapted to match a shape of the inner cavity 4 of the blade 1 at the level of the inner end 11 of the blade 1, the inner cavity 4 having a larger dimension which increases along the thickness direction Y near the inner end 11 of the blade 1.

[0084] Alternatively or additionally, in the first embodiment and / or in the second embodiment, several folds 61 may have different widths PL.

[0085] The reinforcement 6 is delimited radially by an internal border and an external border. opposite the inner edge. A distance, for example an average distance, between the inner edge and the outer edge of the reinforcement 6, corresponds to a height of the reinforcement 6. The inner edge of the reinforcement 6 can be arranged at the level of the opening 5. The reinforcement 6 can extend between the inner edge and the outer edge over at least part of the height of the root 14 of the blade 1 and where appropriate over at least part of the height of the blade 1.

[0086] The height of the reinforcement 6 may be greater than 3% of the height of the blade 1, for example greater than 5% of the height of the blade 1, for example greater than 10% of the height of the blade 1. The height of the reinforcement 6 may be less than 50% of the height of the blade 1, for example less than 25% of the height of the blade 1, for example less than 15% of the height of the blade 1, for example less than 10% of the height of the blade 1. By way of non-limiting example, the height of the reinforcement 6 may be between 5% and 15% of the height of the blade 1.

[0087] In a first embodiment, the reinforcement 6 extends below, that is to say in a position radially more internal than, the secondary flow line Fs delimiting the flow space of the secondary flow of the turbomachine 100. Thus, the reinforcement 6 extends in only a part of the root 14 of the blade 1. The stiffness of the blade 1 is therefore increased at the root 14 of the blade 1 and the mass impact due to the presence of the reinforcement 6 on the blade 1 is limited. For example, the height of the reinforcement 6 may be less than 50 mm. The height of the reinforcement 6 may be less than approximately 10% of the height of the blade 1, or even less than approximately 5% of the height of the blade 1, or even less than approximately 3% of the height of the blade 1.

[0088] In a second embodiment, the reinforcement 6 extends in a portion of the root 14 of the blade 1 and in a portion of the blade 13. An upstream end of the outer edge of the reinforcement 6, i.e. an end of the reinforcement located on the side of the leading edge 8 of the blade 1, extends above, i.e. in a position radially more external than, the secondary flow line Fs at the leading edge 8 of the blade 1. A downstream end of the outer edge of the reinforcement 6, i.e. an end of the reinforcement located on the side of the trailing edge 9 of the blade 1, extends below, i.e. in a position radially more internal than, the secondary flow line Fs at the trailing edge 9 of the blade 1. Thus, the stiffness of the blade 1 is increased at the root 14 of blade 1 and at the leading edge 8 of blade 1, where a large part of the stresses are located, while limiting the mass impact on blade 1 including reinforcement 6.For example, the height of the reinforcement 6 may be between 50 mm and 100 mm. The height of the reinforcement 6 may be between approximately 3% and approximately 20% of the height of the blade 1, for example between approximately 10% and approximately 15% of the height of the blade 1.

[0089] In a third embodiment, the reinforcement 6 extends into the foot 14 of the blade. 1 and in at least a portion of the blade 13 of the vane 1, an outer edge of the reinforcement 6 extending radially above, i.e. in a position radially more external than, the secondary flow line Fs. Thus, the reinforcement 6 extends in the root 14 of the vane 1 over the entire height of the root 14 of the vane 1, and further extends in the blade 13 of the vane 1, over at least a portion of the height of the blade 13, or even over substantially the entire height of the blade 13. Thus, the stiffness of the vane 1 is further increased, both at the root 14 of the vane 1 and at the leading edge 8 and the trailing edge 9 of the blade 13. For example, the height of the reinforcement 6 may be greater than 100 mm. The height of the reinforcement 6 may be greater than approximately 5% of the height of the blade 1, or even greater than approximately 10% of the height of the blade 1, or even greater than approximately 20% of the height of the blade 1, or even greater than approximately 50% of the height of the blade 1. Filling material

[0090] The blade 1 may further comprise a filling material 41 arranged in the inner cavity 4 radially between the reinforcement 6 and the outer end 12 of the blade 1. The filling material 41 thus extends radially above the reinforcement 6, i.e. in a position radially more external than the reinforcement 6, at a distance from the opening 5. The filling material 41 may be arranged against the reinforcement 6, i.e. in contact with the outer edge of the reinforcement 6.

[0091] The filling material 41 may have a density lower than a density of the reinforcement 6 and / or lower than a density of the composite material of the outer skins 2, 3, the filling material 41 being inserted into a hollow zone of the blade 1 which is not a structural zone and therefore does not need to be reinforced. The filling material 41 may have, for example, a density of the order of a hundred kg / m3 and a stiffness of the order of a hundred MPa. The filling material 41 may be integrated into one or more filling pieces, each filling piece being adapted to be arranged in the inner cavity 4 of the blade 1.

[0092] The filling material 41 may for example be a foam, such as a foam of organic origin (polyethacrylimide, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyetherimide (PEI), polyvinyl, carbon, polyisocyanurate, polyurethane, etc.) or metallic (in particular aluminum alloy), or even a honeycomb of the Nomex® type (comprising aramid fibers calendered into sheets and covered with phenolic resin), Kevlar, glass fibers or even aluminum.

[0093] The filling material 41 may be arranged only in the blade portion of the inner cavity 4, in particular when the reinforcement 6 extends throughout the root portion of the inner cavity 4 and in a portion of the blade portion of the inner cavity 4. The filler material 41 may extend into only a portion of the blade portion of the inner cavity 4, or into the entire blade portion of the inner cavity 4, in particular when the reinforcement 6 extends into only a portion of the root portion of the inner cavity 4. The filler material 41 makes it possible to stiffen the outer skins 2, 3 and / or to give the outer skins 2, 3 the final shape of the blade 13, with minimal impact on the mass of the blade 1. Reinforcement manufacturing process

[0094] A method of manufacturing a reinforcement 6 as described above for a blade 1 of a turbomachine 100 as described above comprises the following steps: El: Cutting a set of plies 61 in a carbon mat, each ply 61 having a length PI, a width PL and a thickness Pe, at least two of the plies 61 of the set having different lengths PI and / or widths PL; E3: Stacking of the plies 61 of the assembly by superimposing a ply 61 on an adjacent ply 61 along a direction of the thickness Pe of the plies 61, so as to create a stack having a profile of variable dimensions; and E4: Compaction of the stack of folds 61.

[0095] The method described below generally has the same advantages as those described concerning the reinforcement 6 described above. The method makes it possible in particular to quickly create a reinforcement 6 having a complex geometry.

[0096] Furthermore, the reinforcement 6 is made from a carbon mat, which makes it possible to produce a rigid part with a complex geometry.

[0097] The carbon mat is in the form of a rectangular support, possibly rolled into a roll, having a certain thickness. Thus, the carbon mat may be a roll formed by a strip of non-woven fibers, for example a strip of non-woven carbon fibers, comprising a small proportion of a polymer, for example a thermostatic or thermosetting polymer, acting as a binder. The fibers are mixed with the binder, calendering being carried out where appropriate up to a temperature greater than or equal to the glass transition temperature of the binder material. The binder ensures the cohesion of the fibers and the strength of the strip. The carbon mat may be a recycled product manufactured from carbon fiber scraps. The thickness Pe of a ply 61 may correspond to the thickness of the carbon mat.

[0098] The step E1 of cutting plies 61 in the carbon mat may correspond to cutting with scissors. However, such cutting with scissors is very long. Alternatively, the step E1 of cutting plies 61 in the carbon mat may correspond to cutting with water jets. Such cutting with water jets makes it possible to facilitate the manufacture of the reinforcement 6 and to lighten the target manufacturing range and to obtain a clean, heat-free and repeatable cut of the mat, without degrading the fiber, in order to be able to drape plies 61 of carbon mat subsequently.

[0099] The set of plies 61 cut in step E1 can then be prepared for use in a clean room. Step E3 of stacking the plies 61 of the set is carried out in a clean room. The stacking step E3 makes it possible to obtain a reinforcement 6 whose dimensions correspond substantially to the dimensions of the internal cavity 4 of the blade 1 located between the two composite skins 2, 3, that is to say to obtain a reinforcement 6 which can have large variations in thickness.

[0100] The plies 61 may be stacked during step E3 in a forming mold. The forming mold may be a single forming mold having a counterform relative to the reinforcement 6 to be created. The plies 61 are then superimposed directly in the forming mold, to fill the forming mold so as to create the reinforcement 6 having the desired geometry. Alternatively, the forming mold may consist of two forming half-molds, each having a counterform corresponding substantially to one half of the shape of the reinforcement 6 to be created. A first portion of the plies 61 of the assembly are stacked on top of each other in a first forming half-mold, and a second portion of the plies 61 of the assembly are stacked on top of each other in a second forming half-mold.The first forming half-mold forms a wedge on which a first ply 61 is arranged, a second adjacent ply 61 being superimposed on the first, and so on for all the plies 61 of the first part of the assembly. In the same way, the second forming half-mold forms a wedge on which a first ply 61 is arranged, a second adjacent ply 61 being superimposed on the first, and so on for all the plies 61 of the second part of the assembly. One of the first and second forming half-molds is then turned over and aligned with respect to the other, the two forming half-molds being arranged opposite each other. Then, the two forming half-molds are assembled to form a complete forming mold having a counterform with respect to the reinforcement 6 to be created.

[0101] The compacting step E4 makes it possible to compact the stack of plies 61 to obtain the desired final dimensions of the reinforcement 6 and ensure the cohesion of the plies 61 of the stack. The mold is tightened, for example under pressure. The plies 61 can be compacted during step E4 in the forming mold.

[0102] The method of manufacturing the reinforcement 6 may further comprise the following steps: E2: Humidification of the folds 61 after the cutting step E1 and before the stacking step E3; and E5: Drying of the stack of compacted 61 folds during step E4.

[0103] Step E2 of humidifying the plies 61 makes it possible to soften the carbon mat decouples and thereby facilitate the shaping and compacting of the plies 61 once stacked, making it possible to obtain lower fiber-to-fiber friction.

[0104] The drying step E5 makes it possible to remove the water added during the humidification step. The drying makes it possible to shape and bind the plies 61 stacked together so that the stack of plies 61 holds together. Thus, the drying makes it possible to give cohesion to the fibers between them, which makes it possible to have a rigid reinforcement 6, therefore to stiffen the preform of the blade 1 as best as possible.

[0105] The compacted stack of plies 61 may be mounted for drying, the mounting possibly including a vacuum cover, valves, felt, etc. Drying may be carried out in an oven or autoclave.

[0106] The compacted stack of plies 61 may be placed in a drying mold, or alternatively the drying mold may correspond to the forming mold used for stacking the plies 61 during step E3 and for compacting the plies 61 during step E4.

[0107] Drying step E5 can be carried out for a duration of approximately 6 hours and at a temperature of approximately 100°C to 120°C. Alternatively, drying step E6 can be carried out for a duration of approximately 12 hours and at a temperature of approximately 100°C to 120°C. The cycle of drying step E5 can be adapted according to the nature of the binder and the ventilation necessary to evacuate the water introduced during the humidification step.

[0108] The method may further comprise a step E6 of demolding the compacted, if necessary dried, stack of plies 61. The demolding may be carried out cold, i.e. at room temperature, so that the enzyme which is in the fibers is well stiffened. Blade manufacturing process

[0109] A blade 1 as described above may be obtained using the following manufacturing method, which is illustrated as a non-limiting example in [Fig.7]. This is not, however, limiting, and other methods may be envisaged for producing such a blade 1. The manufacturing method of the blade 1 may comprise the following steps:

[0110] Production of a composite preform of the composite blade 1 during a step E0, said preform comprising a first outer skin 2 and a second outer skin 3 made of composite material connected to each other at an outer end 12 of the blade 1, the first skin 2 comprising a first inner end portion 21, the second skin 3 comprising a second inner end portion 31, the first inner end portion 21 and the second inner end portion 31 being spaced apart from each other so as to delimit between them an inner cavity 4 of the blade 1 opening into an opening 5 at an inner end 11 of the blade 1, the inner end 11 being radially opposite the outer end 12;

[0111] Manufacturing of a reinforcement 6 by means of a method for manufacturing a reinforcement 6 such as described above, the reinforcement 6 having dimensions substantially equal to the dimensions of the interior cavity 4 at the level of the opening 5;

[0112] Placing the reinforcement 6 in the interior cavity 4 of the blade preform 1 so as to plug the opening 5; and

[0113] Injection of resin into the assembly comprising the blade preform 1 and the reinforcement 6 during a step Eli.

[0114] This method makes it possible to inject the reinforcement 6 at the same time as the rest of the blade 1. Thus, the reinforcement 6 is bonded to the skins 2, 3 of the blade 1 without the use of glue or surface treatment. In addition, the reinforcement 6 ensures good compaction of the skins 2, 3 of the blade 1 in the radii during shaping, ensuring the desired fiber volume ratio in the radii.

[0115] The fiber preform of the blade 1 can be produced during step E0 for example by three-dimensional weaving or knitting. In an exemplary embodiment, the fiber blank is woven in three dimensions with the creation of a delinking in order to obtain the two skins 2, 3 and the inner cavity 4, as described above concerning the blade 1. The two skins 2, 3 are monolithic at the level of the head 12 of the blade 1, the leading edge 8 and the trailing edge 9 of the blade 13. The inner cavity 4 is open at the level of the root 14 of the blade 1 and extends into the blade 13.

[0116] The manufacture of the preform of the blade 1 may comprise a step of cutting surface threads of the woven preform (in English, “Trimming”), in particular when threads of the preform remain non-woven and protrude.

[0117] A filling material 41 may be placed in the interior cavity 4, following the placement of the reinforcement 6 in the interior cavity 4 or prior to this placement.

[0118] During step E10, the reinforcement 6 can be placed in the interior cavity 4, for example pressing against the filling material 4L. The reinforcement 6 blocks the interior cavity 4 of the blade 1 at the opening 5.

[0119] The assembly formed by the fiber preform, the filling material 41 and the reinforcement 6 can then be placed in an injection mold. The injection mold can have a counterform of dimensions corresponding substantially to the dimensions of the final molded blade 1, namely the desired blade 13 and root 14 of the blade 1. The mold is then closed, for example by a wall which blocks the opening 5, in order to carry out the injection.

[0120] The resin injected during step Eli, which forms the “matrix” of the composite material, is generally a plastic material. The resin is injected into the injection mold so as to impregnate the fibrous reinforcement of the skins 2, 3, the filling material 41 and the reinforcement 6.

[0121] The injection of the matrix can be carried out by an injection technique of the type RTM or VARRTM. In the case of a plastic material, the injected matrix is, for example, a thermosetting liquid composition containing an organic precursor of the matrix material. The organic precursor is usually in the form of a polymer, such as a resin, possibly diluted in a solvent. In a manner known per se, the plastic material is then heated so as to cause its polymerization, for example by crosslinking. For this purpose, the injection mold is placed in an oven. The resulting part can then be demolded from the injection mold.

[0122] Optionally, a leading edge 8 can be inserted into the upstream part of the preform of the blade 1. An outer layer forming the leading edge 8 is then placed on the preform to achieve the pairing of the leading edge 8. Then, the leading edge 8 is passed through the autoclave to be bonded to the preform.

[0123] Then, one or more stages of various finishing and / or completions can be carried out. For example, the demolded part can be machined to remove excess lengths and obtain a part having the desired shape, despite possible shrinkage of the fibers of the fiber reinforcement during the polymerization of the plastic material. The sacrificial thicknesses are in particular machined to obtain the reference surfaces of the root 14 of the blade 1. Through passages are also machined in the skins 2, 3 to receive the fixing system. If necessary, counterbores are also machined around the through passages.

Claims

Claims

1. Reinforcement (6) for a blade (1) of a turbomachine (100), the blade (1) comprising a first outer skin (2) and a second outer skin (3) made of composite material connected to each other at an outer end (12) of the blade (1), the first skin (2) comprising a first inner end portion (21), the second skin (3) comprising a second inner end portion (31), the first inner end portion (21) and the second inner end portion (31) being spaced apart from each other so as to delimit between them an inner cavity (4) of the blade (1) opening into an opening (5) at an inner end (11) of the blade (1), the inner end (11) being radially opposite the outer end (12), wherein the reinforcement (6) is adapted to be arranged in the inner cavity (4) so ​​as to plug the opening (5), and in which the reinforcement (6) comprises a stack of folds (61),each ply (61) having a length (PI), a width (PL) and a thickness (Pe), a ply (61) being superimposed on an adjacent ply (61) in a stacking direction (De) corresponding to a direction of the thickness (Pe) of the plies (61), at least two of the plies (61) of the stack having different lengths (PI) and / or widths (PL) so that the reinforcement (6) has a profile of variable dimensions, the reinforcement (6) having a rigidity greater than 15 (+ / -5) GPa in a radial direction (R) of the blade (1).,

2. Reinforcement according to claim 1, in which the stack of plies of the reinforcement (6) comprises a first ply (611) having a first length (Ply) and a second ply (612) having a second length (P12) strictly less than the first length (Ply), and in which: - the second ply (612) is arranged closer to a center of the reinforcement (6) than the first ply (611), the stacking direction (De) being adapted to correspond to a thickness direction (Y) of the blade (1), or in which - the first ply (611) is adapted to be arranged closer to the inner end (11) of the blade (1) than the second ply (612) when the reinforcement (6) is arranged in the inner cavity (4) of the blade (1), the stacking direction (De) being adapted to correspond to a height direction (R) of the blade (1).

3. A blade (1) of a turbomachine (100), comprising a first outer skin (2) and a second outer skin (3) made of composite material connected to each other at an outer end (12) of the blade (1), the first skin (2) comprising a first inner end portion (21), the second skin (3) comprising a second inner end portion (31), the first inner end portion (21) and the second inner end portion (31) being spaced apart from each other so as to delimit between them an inner cavity (4) of the blade (1) opening into an opening (5) at an inner end (11) of the blade (1), the inner end (11) being radially opposite the outer end (12), the blade (1) further comprising a reinforcement (6) according to claim 1 or claim 2, wherein the reinforcement (6) has dimensions corresponding to the outer end (12) of the blade (1), the inner end (11) being radially opposite the outer end (12), the blade (1) further comprising a reinforcement (6) according to claim 1 or claim 2, wherein the reinforcement (6) has dimensions corresponding to the outer end (12) of the blade (1), the inner end (11) being radially opposite the outer end (12), the blade (1) further comprising a reinforcement (6) according to claim 1 or claim 2, wherein the reinforcement (6) has dimensions corresponding to the outer end (12) of the blade (1), the outer end (1 ... substantially to the dimensions of the interior cavity (4) at the opening (5),the reinforcement (6) being arranged in the interior cavity (4) so ​​as to block the opening (5).,

4. A blade (1) according to claim 3, comprising a blade (13) with an aerodynamic profile suitable for being placed in an air flow when the turbomachine (100) is in operation in order to generate lift, and a root (14) configured to be fixed to the hub of a blade comprising the blade (1) at the inner end (11) of the blade (1), wherein the first inner end portion (21) and the second inner end portion (31) are adapted to together define outer walls of the root (14) and at least a portion of the blade (13) of the blade (1), such that the inner cavity (4) comprises a root portion and a blade portion, and wherein the reinforcement (6) comprises a root portion disposed in the root portion of the inner cavity (4) and a blade portion disposed in the blade portion of the inner cavity (4).

5. A blade (1) according to claim 3 or claim 4, further comprising a filler material (41) disposed in the inner cavity (4) radially between the reinforcement (6) and the outer end (12) of the blade (1).

6. Unducted turbomachine (100), comprising: - a casing (101); - a fan (200) having a fan hub (201) (200) and peripheral fan blades (202) (200), integral with the fan hub (201) (200), the fan hub (201) (200) having a part downstream (203) of hub (201) which is surrounded by an inner surface (102) of an upstream part (103) of the casing (101) and which protrudes from the upstream part (103) of the casing (101), the hub (201) of fan (200) being rotatably mounted relative to the upstream part (103) of the casing (101) around the longitudinal axis (X); and - at least one rectifier blade (1) according to any one of claims 3 to 5, said blade (1) being located downstream relative to the peripheral blades (202) of fan (200), said blade (1) being mounted on an outer surface of the upstream part (103) of the casing (101) at an inner end of the blade (1), the reinforcement (6) being arranged at the inner end of the blade (1).

7. Method for manufacturing a reinforcement (6) according to claim 1 or claim 2 for a blade (1) of a turbomachine (100), comprising the following steps: E1: Cutting a set of plies (61) in a carbon mat, each ply (61) having a length (PI), a width (PL) and a thickness (Pe), at least two of the plies (61) of the set having different lengths (PI) and / or widths (PL); E3: Stacking the plies (61) of the set by superimposing a ply (61) on an adjacent ply (61) along a direction of the thickness (Pe) of the plies (61), so as to create a stack having a profile of variable dimensions; and E4: Compacting the stack of plies (61).

8. Manufacturing method according to claim 7, further comprising the following steps: E2: Humidification of the plies (61) after the cutting step E1 and before the stacking step E3; and E5: Drying of the stack of plies (61) compacted during step E4.

9. Manufacturing method according to claim 7 or claim 8, wherein the plies (61) are stacked during step E3 in a forming mold, the plies (61) are compacted during step E4 in the forming mold, and wherein the method further comprises a step E6 of cold demolding the compacted stack of plies (61).

10. Method for manufacturing a blade (1) of a turbomachine (100) according to any one of claims 3 to 5, comprising the following steps: Production of a composite preform of the composite blade (1) (E0), said preform comprising a first outer skin (2) and a second outer skin (3) made of composite material connected to each other the other at an outer end (12) of the blade (1), the first skin (2) comprising a first inner end portion (21), the second skin (3) comprising a second inner end portion (31), the first inner end portion (21) and the second inner end portion (31) being spaced apart from each other so as to delimit between them an inner cavity (4) of the blade (1) opening into an opening (5) at an inner end (11) of the blade (1), the inner end (11) being radially opposite the outer end (12); Manufacture of a reinforcement (6) by means of a method according to any one of claims 7 to 9, the reinforcement (6) having dimensions substantially equal to the dimensions of the interior cavity (4) at the opening (5); Placing the reinforcement (6) in the inner cavity (4) of the blade preform (1) so as to plug the opening (5); and Injection of resin into the assembly comprising the blade preform (1) and the reinforcement (6) (El 1).

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